Even lower projections for longer term sea level rise would wipe out more than 15% of Pacific islands, according to research quoted by a U.N. report to be published next week.

In the shorter term, small island states can better prepare for extreme events including storms and sea level rise through coastal protection and development of less vulnerable land.

The U.N. report, leaked online, is the second of a three-part publication which the Intergovernmental Panel on Climate Change (IPCC) produces every five to six years on the threats posed by global warming.

Even in its first such publication in 1990, the IPCC warned of an existential threat to small island states, saying that a 1 metre sea level rise ‘would render some island countries uninhabitable’.

The latest review published research which suggested a widespread threat beyond this century.

A comprehensive study of 12,983 islands of all sizes above 2.5 hectares across the Pacific Ocean, including the Philippines and Hawaiian Islands, found that some 15 to 62% of islands would entirely disappear under sea level rise ranging from 1 to 6 metres.

That corresponded to 1-9% of the total area studied, found the article published last year in the journal Global Change Biology.

The IPCC will next week also quote research that a 0.5 to 2 metre sea level rise could displace between 1.2 and 2.2 million people from islands in the Caribbean, Indian Ocean and Pacific Ocean, before allowing for adaptation such as coastal protection.

Next week’s IPCC report quotes research that the world has already locked in 1.3 metres sea level rise over the next two thousand years, as ice sheet melt and warmer seas expand.

Other research, also quoted in the report, calculated that a long-term temperature rise of 2 degrees Celsius above pre-industrial levels would lead to a median global sea level rise of 4.8 metres over the next two thousand years.

Extreme events

Most inundation of islands presently is linked to earthquakes, storm surges and swell waves as well as sea level rise, the IPCC said.

For example, from 2002-2004 a village was relocated inland in remote islands in Vanuatu in the southwest Pacific, following inundation which was a result of both tectonic subsidence and sea level rise.

And in 2008, inundation which displaced some 63,000 people in Papua New Guinea and the Solomon Islands was caused by large swell waves coupled with unusually high sea levels linked with the natural El Nino weather pattern, which leads to relatively more rainfall over the Pacific Ocean compared with over land.

Island states could prepare for such events through more thoughtful development, where recent rapid urbanisation and growth in tourism has seen increasing settlement of more vulnerable coastal land.

The IPCC found that most Pacific atoll islands had not seen net inundation yet.

“Historical shoreline position change over 20 to 60 years on 27 central Pacific atoll islands showed that total land area remained relatively stable in 43 per cent of islands, whilst another 43 per cent had increased in area, and the rest showed a net reduction in land area,” the IPCC said, reporting research published in 2010.

However, one more recent study in the Marshall Islands showed that overall net accretion before 2004 had since switched to net erosion in 17 of a group of 18 islands.

Long-term

Sea levels rise both as oceans expand as a result of global warming, and as more water is added to the sea from melting glaciers and polar ice sheets.

Vulnerable islands include states and territories in the tropics of the southern and western Pacific Ocean, central and western Indian Ocean, the Caribbean Sea, and the eastern Atlantic off the coast of west Africa, as well as in the Mediterranean.

The IPCC reported last year on the physical evidence for climate change, and projected sea level rise this century of 0.26 and 0.82 metres, according to scenarios which ranged from rapid cuts in carbon dioxide emissions to continuing rising emissions through the century.

In the long term, global sea levels are expected to rise by more than 1 metre as ice sheets continue to melt regardless of trends in carbon emissions and warming, and by much more if carbon emissions continue to rise for the next few decades.